Automatic telephone system



Dec. 26, 1933.

A. FLAD AUTOMATIC TELEPHONE SYSTEM Filed July 18, 1932 Patented Dec. 26,

' iii? AEJTDMATIC TELETHONE SYSTEM Artur Fla-cl, BcrlinyGermany,assignor to Siemens lilalslie Alrtienges'ellschaft,

Wernerwerk Siemensstadt, near Berlin, Germany Application July is, 1932,Serial No. 623,036, and

in Germany September 26, 1931 I 1 15 Claims. (01. Nile-18) The presentinvention relates to circuit arrangements for testing in telephonesystems pr vided with two-wire switches and two-wire junction lines. Inknown arrangements of this type complicated wiring is necessary for thispurpose due to the fact that potential must be applied to the twospeaking leads all the time-e-that is to say, both prior to as well asduring a connection. loConsequently, for example, quite'a number ofdifierent equalizing'resistances have to be inserted in the individualbranches to set up the necessary current ratios in the multiply wiredselecting circuits requiredto prevent double connections. In addition,this type of arrangement involves considerable difficulties in thetransmission of switching operations; particularly after a connectionhas'been completed, such as, for example, metering, due to theabove-mentioned fact that a potential is permanently applied to both theleads and consequently cannot be used for such switching operationsunless-special steps to this end aretaken." f

The present invention eliminates these difii- .culties in a simplemanner by causing the junction lines to be tested in the switcheswhether idle or busy with the aid of a switching means disposed betweenthe two speaking leads and caused to function by means of a gasdischarge or neon tube influenced over said junction lines if idle.

The invention with advantage makes use of the arrangement known per sein which the release is effected with the aid of a relay to be energizedtwo leads of 'the junction line during operation, with the result thatsaid junction-line can be adequately guarded against seizure switchesand whereby itis possible to transmit switching operations over the twoleads of the line. 7 7 An embodiment of the invention is shownin theaccompanying drawing. I

A connection between the subscribers Tn and Tnl will now be described inconjunction with Fig. 1. Switching apparatus of no importance for theunderstanding, of the invention has not been shown. When the subscriberTn lifts his receiver, his preselector VW startsoperating in knownmanner and hunts for a line leading to an idle first group selector.When found, relay R in the preselector VW and relay C 'in'the firstgroup selector IGW are energized in the following circuit: earth,battery, windings I and II of relay T, c-wiper of the preselector VW,winding I of over a neon lamp. This completely releasesthe from otherrelay C, off-normal contact 17c, earth. Relay T brings the preselectorto rest on the idle line in known manner and switches through the twospeaking leads. Relay'ZR, which lies parallel with winding II of relayTis not energized inthe 0 test circuit. After the two speaking leadshave been switched through, the impulse-receiving relay A in the firstgroup selector IGW operates over windings I and II and the closedsubscriber s line loop. Relay 0 is placed in the following 5 lookingcircuit: earth, battery, contact 30, winding II ofrelay C, contact 5a,winding I of relay V, earth. Relay V also operates in this circuit.RelayC, by closing its contact 170 prepares'the vertical steppingcircuit, by closing contact 250 it prepares the test circuit and byclosing contact 90 prepares for repeating impulses. Relay V, by closingits contact 241) prepares a locking'circuit for the test relay P and byclosing its contact 1922 the rotary stepping circuit. 1 J 7 Bymanipulating his dial, the subscriber Tn now transmits the first impulseU series, which causes the subscribers line loop to be alternativelyopened andclosed in known manner and consequently also the-circuit'forrelay A in the first group selector IGW to be intermittently opened andclosed. Relay A operates accordingly' and transmits the impulses to thevertical magnet over the following route: earth, contacts 170, 16a,rotary off-normal contact 1520, winding 35 of vertical magnet l-I,battery, earth. Due to the opening of contact 5a on the first relapse ofrelay A, the short circuit for winding II of relay P is removed. Thisrelay then remains energized during the impulse transmission due to itswinding I being short circuited by means of the closed .contacti43p.After the first vertical step the circuit for the release magnet M isprepared by .the closing of the off-normal contact 44k and the rotarystepping circuit also is prepared due tothe closing of the off-normalcontact 21k. Further, due to the opening of the off-normal contact 170'on the first vertical step, the circuit for winding 1' of relay 0 iscut off. The circuit for relay T r in the preselector VW, however, ismaintained over earth, resistance Wi, contact 47m of'the release magnetM. Relay A is re-energized at the end of the first impulse series. Bymeans of contact 5a it permanently short circuits winding II of relay P,which consequently relapses and closes. 5 the following circuit for therotary magnet of the first group selector IGW: earth, interrupter RU,

off-normal contact 21k,- contacts '20p, 19',

winding of rotarymagnet D,- battery, earth.

The first group selector hunts freely for an idle line in the level towhich it has been raised by the first impulse series. This line may befound to be the junction line VL which leads to a second groupselectorIIGW. When found, the following circuit for the neon lamp GL isclosed: earth, contact 2701 in the second group selector IIGW, b-lead ofthe junction line VL, b-wiper of the first group selector, contact 250,neon lamp GL, winding I of relay P, a-wiper of the first group selector,a-lead of the junction line VL, contact 2601, windingII of relay C1 inthe second group, selector IIGW, battery, earth. The battery B has asufficiently high potential to light the neon lamp; for example, 90volts. When this neon lamp has been lighted, relay C1 in the secondgroup selector IIGW and relay P in the first group selector IGW operatein the aforesaid circuit. Relay P in the first group selector brings theswitch to rest by opening its contact 201). It is then placed in thefollowing locking circuit by closing its contact 23p: earth, winding IIIof relay P, rotary oft-normal contact 22w (closed on the first rotarystep), contacts 23p,

241), battery, earth. The closing of contacts 10p and 11p switch throughthe two speaking leads to the second group selector.

' As mentioned above, relay C1 in the second group selector IIGWoperates, is disconnected from the speaking leads due to the opening ofcontacts 2601 and 2701 and, as before, is placed in the followinglocking circuit: earth, contacts 3401, 33b1, winding I of relay C1,battery, earth. The closing of contact 2901 connects theimpulse-receiving relay A1 to the a-lead. The closing of contact 3201places winding I of the test relay P which lies in series with the neonlamp GL1 between the two speaking leads. A locking circuit for windingII of the test relay P1 is pre- .pared by the closing of contact 3701.The closing of contact 2801 causes the release relay B1, which isconnected in series with the neon lamp GL2, to be connected to theb-lead.

,On the succeeding impulse series for the setting of the second groupselector IIGW, relay A of the first group selector IGW is againintermittently energized and de-energized; By closing its contact lot itapplies earth intermittently to the a-lead and thus causes theimpulse-receiving relay A1 in the second group selector IIGW to operateover the following circuit: earth, contacts 7a, 90, 10p, a-wiper of thefirst group selector, .a-lead of the junction line VL, contact 29c1',

winding of relay A1, rotary ofi-normal contact 45w, battery, earth.Relay A is energized and transmitsthe impulses in known manner to thevertical magnet (not shown) of the second group selector. At the end ofthe impulse series the group selector hunts for an idle line leading toa final selector. The impulse circuit for this operation being of noimportance for the understanding of the present invention, it has beenomitted. When the group selector has found a line leading to an idlefinal selector, for example, the shown final selector LW, the followingcircuit is closed for the neon lamp GL1: earth, contact 3902, b wiper ofthe second group selector IIGW, winding I of the test relay P1, neonlamp GL1, contact 3201, a-wiper of the second group selector IIGW,contact 3802, winding of relay C2, battery B3, earth. The battery B3applied to the final selector LW has a sufficiently high. voltage tolight the neon lamp GL1. After said lamp has been lighted, relays C2andPl operate in this circuit. Relay P1 brings the second group selectorto rest in known manner and, by'closing its contacts contacts 3701,36121, rotary off-normal contact 35w, winding 11 of relay P1, battery,earth.

As previously mentioned, relay C2 in the final selector is caused tooperate. This relay, by opening its contacts 3802 and 3902, isdisconnected from the speaking leads after having been placed in alocking circuit in the manner described for the first and second groupselectors. The closing of contact 4202 connects the release relay B2,which lies in series with the neon lamp GL3, to the b-lead. Theimpulseseries for the setting of the final selector LW to the requiredsubscribers line are now transmitted. The circuits concerned in thisoperation are or" no importance for the invention and, th refore, havenot been shown. When the subscriber Tnl answers, the feeding bridgerelay A2 operates in the following circuit: earth, winding I of relayA2, b-wiper of the final selector LW, line loop for the subscriber Tnl,d-wiper of the final selector LW, winding II of relay A2, battery,earth. A potential is now applied to the b-lead over the closed contactila2 and position 1070f a not showncontrol switch and earth in the samemanner is applied to the a-lead over the closed contact 40a2 and thecontrol switch set to positionlO. When the subscriber Tn, after havingfinished the call, replaces his receiver, relay A in the first.

group selector IGW restores, due to the inter ruption of the subscribersline loop. Relay A, by means of its contact 4a short circuits winding IIof relay 1. This relay relapses and by opening its contact 30 I of relayV, which remains energized in thefollowing circuit: earth, contact 4M2,control switch set to position it, a-wipe'roi' the second group selectorIIGW, contact BGpl, a-lead of the him opens the circuit for winding tionline VL, a-wiper of ti e first group selector IGW, contacts 192 6c,winding II of relay ,V,'battery, earth. The following circuit for relay.Z'in the first group selector IGW is closed after relay C has released:earth, battery, contact lla2,'control sw' ch set to position 10,b-wiperofthe-second i group selector IIGW, contact I-Elpl, b-wiper oithe first group selector IGW, contacts 11;), 130,

winding of relay Z, off-normal contact 1415, earth.

Relay Z operates and by closing its contact 22 applies direct earth tometering relay ZR in the preselector VW to be energized due tothe'increased voltage. On the aticn of reiay'Z, winding II of relay V isshort circuited by meansof contact 82, so that it therefore releaseswith slow action. During its release period the following circuit forthe release relay B1 in the second group selector IIGW and relay E2 inthe final selector LW is closed: earth,

alternating current source of supply WQ, contacts lip, b-wiper of thefirst group selector IGW,-

b-lead of the junction line VL, contact 2801, neon GL2, winding of relayBl, battery, earth and parallel thereto, contact 31301, vb-wiper of thesecond group selector IEGW, contact i202, neon lamp GL3, winding ofrelay B2, battery, earth. The neon lamps GL2 and GL3 are lighted due tothe additional alternating current from the alternating current sourceof supply WQ and consequently generate aidirect current for relays B1and B2. This circuit is opened by contact lip on the release of relay Pin the first group selector IGW. Further, on the relapse of relay 'P,the following circuit for the release magnet M is closed: earth,off-normal contact 44k, contacts the c-lead, thus causing the (13p, "18,winding of the release magnet M, battery, earth. The first groupselector IGW is restored to normal position when the release magnet M isenergized. Contact 47m then opens the test circuit to the preselector VWand 'in this manner initiatesthe release of the latter switch. T

On the energization of relay B1 in thesecond group selector IIGW thelocking circuit for winding I of relay C1 is interrupted due to theopening of contact 33111;. Relay C1 therefore restores and by openingits contact 3701 breaks the locking circuit for winding II of the testrelay P1,. so that it relapses andat its contacts 30101 and 31311 opensthe two speaking leads and in a manner similar to that described forrelay P in the first group selector IGW initiates the release of thesecond group selector IIGW.

Due to the energization of relay B2in the final selector LW the lockingcircuit for relay C2 is opened, causing this relay to release and soinitiate the release of the final selectorLW in known manner after thesubscriber Tnl'has replaced his receiver. I 7' A further form ofconstruction of the invention is shown in Fig.2, in which relay C1 inthe second group selector IIGW is not disconnected from the two speakingleads by means of its own contacts.

. relay C1, moreover, is not cut off from said speaking leads untilafter the first vertical step on the part of the switch at which theoff-normal contacts 54k and 55k are opened. In order to prevent amultiply wired switch from testing the seized junction line VL betweenthe actual seizure and the first impulse, the test relay P in the firstgroup selector IGW short circuits the neon lamp GL over its own contact52p and the choke Dr. The

test relay P of another testing switch cannot be operated due to thefact that the voltage drop at the multiply wired contacts of the switchis so great in consequence of the current passing over contact 52p andthe choke Dr that the voltage for the lighting of the neon lamp of aparallel testing switch is insufficient.

What is claimed is:

1. In an automatic switch, two talking conductors, means for causing theswitch to'hunt for an idle trunk, and means including a gas dischargetube connected across said conductors for stopping the switch when anidle trunk is found. a

2. In a telephone system, an automatic switch, a group of trunks, meansfor maintaining a definite potential on each trunk while idle, means formoving the switch over the group of trunks,

means including a neontube adapted to flashover at said defintepotential for testing the trunks passed over for their busy or idlecondition, and means controlled by said last means for stopping theswitch on an idle trunk. V

3. In a telephone system, an automatic switch, a group of trunks, eachtrunk having normally connected thereto a source of current of aparticular potential, means for moving the switch over the group oftrunks, means including a neon tube adapted to flash-over at saidparticular po tential for testing the trunks passed over for their busyor idle condition, and means responsive to said tube flashing-over forcausing the switch to seize a trunk and for disconnecting said'source ofcurrent therefrom.

4. In an automatic switchequipped withtwo line wipers, means forautomatically moving the Wipers over a-group of trunks, a relay and agas discharge device connected across the linewipers in series, saiddevice controlling the energization means for causing the switch to huntfor an idle trunk, a relay and a' neon tube connected in series acrossthe outgoing conductors, means for op erating the tube and relayresponsive to the finding of an idle trunk, and means controlledby saidrelay forpreventing further huntingby the switch and for connecting-saidincoming conductors to's aid outgoing conduct ors. i I 6. In a telephonesystemfan automatic switch, a test circuitincluding-a neon tube and arelay in said switch, 'a'tr'unk accessible to said switch, a source ofcurrent normallyconnected to said trunk, means for operating the switchinto en gagement with said trunk whereby said current source isconnected to the test circuit tooperate said tube and said relay, andcontacts controlled by said relay foreffecting the seizure of saidtrunk. V I 1 7. In a telephone system, automaticswitches, atrunk, asource of'current of a particular potential normally connected to thetrunk, means for operating one of the switches into engagement with thetrunk, means including a neon tube adapted to flash-over at saidparticular potential for causing the switch to seize said trunk, andmeans responsive to the seizure of the trunk for disconnecting saidcurrent source to prevent a subsequent seizure of the trunk by anotherswitch.

8. In a telephone system, automatic switches, a supervisory relay ineach switch, a trunk accessible to said switches, a source of current ofone potential normally'connected to the trunk, means for operating oneof said switches to extend a connection tothe trunk, means in said oneswitch including a neon tube adapted to flash-over in consequence of theconnection of the switch with said source of current via the trunk forcausing the switch to seize the trunk, means responsive to the seizureof the trunk for disconnecting said current source from the trunk toprevent subsequent seizure by another switch, a second source of currentof a potential ineffecequipped witha pair of'wipers, a trunk comprisingtwo talking conductors accessible at one end to the switch via saidwipers, a relay, and a source of current connected to the other end ofthe trunk conductors, means for operating theswitch to bring said wipersinto engagement with the trunk conductors, a test circuit including aneon tube and said wipers in the switch, said tube being adapted toflash-over in consequence of the connection with said current sourcewhereby the seizure of the trunk and the operation of said relay iseffected, and means controlled by the. re-' layfor disconnecting saidcurrent source from the trunk to mark the trunk busy.

10. In a telephone system, a trunk comprising two talking conductors, arelay, connected to one end of said conductors in series with a sourceof current, means for operating the relay responsive to the seizure ofthe trunk at the other end thereof, and means controlled by the relayfor disconnecting itselfand the current source from the trunk conductorsto prevent a subsequent seizure of the trunk,

ll. In a telephone system,l ines each of which is maintained at onepotential when idle, at another potential during part of the time whenbusy, and at no potential during the remainder of the busy time, andmeans for testing the lines including means effective to draw currentfrom lines on which said one potential is present.

12. In an automatic switch, talking conductors, operating means forselecting a group of trunks, a relay, a neon tube, an impedance, meansfor connecting said relay and said tube in series across said talkingconductors for testing said trunks, contacts controlled by said relayfor stopping the switch on an idle one of said trunks, and contactscontrolled by said relay for shunting said tube with said impedance tomark said one trunk busy.

13. In a telephone system, an automatic switch including two talkingconductors, groups or" trunks accessible to the switch, means fortransmitting a series of impulses to the switch to set the same inselective relation with one of said groups of trunks, means including arelay and a gas discharge tube bridged across the talking. conductors ofthe switch for causing the switch to connect with an idle trunk insaid'one group, and means in the switch for repeating impulses over thetrunk connected with. I

14. In an automatic telephone system, selective switches, means foroperating a plurality of switches-in tandem to establish a two-conductormetallic talking circuit, means for operating other of said switches inattempting connection with said talking circuit, and testing means insaid other switches including neon tubes controlled over the talkingcircuit for preventing 'the'establishment of the attempted connectionswithout interfering with the talking circuit.

15. In an automatic telephone system comprising selective switches inwhich the usual third conductors extending through" and between switchesare omitted, means including a neon tube in each switch whereby thetesting functions are controlled overthe talking conductors withoutinterfering with conversation, and means including a second neon tube ineach switch whereby the release of the switches is controlled over thetalking conductors.

ARTUR. FLAD.

